docs: def insurance_limit(self, loss_type, dummy=None):
          """
          :returns: the limit fraction of the asset cost for `loss_type`
          """
          val = self.calc(loss_type, self.insurance_limits, self.area,
                          self.number)
          if self.calc.limit_abs:  # convert to relative value
              return val / self.calc(loss_type, self.values,
                                     self.area, self.number)
          else:
              return val